Methane fermentation heating value

Klass (1980). Methane fermentation conditions were daily feeding, continuous mixing, 35°C, pH 6.7 to 7.2, 12-day retention time, for kelp, which was 2,1 kg VS/m -day, All biomass was 1.2 mm or less in particle size. The blends are described in detail in the volatile solids (organic matter). HHV is higher heating value. 

Gas made by pyrolysis of biomass, or of municipal solid waste, resembles coal syntehsis gas in composition, and can be produced in the same heating values. Gas made by anaerobic fermentation of biomass is predominantly methane and carhon dioxide. When the carbon dioxide is removed, it is a replacement for natural gas. 

The fermentation is usually continuous it proceeds under sterile conditions, at constant temperature, and is started with a defined starter culture to avoid side products as far as possible. Several processes were developed Shell had originally introduced a process that used methane (natural gas) as the feedstock for SCP production. The microorganisms are cultured in an aqueous medium at temperatures of 42 to 45°C and at a pH value of 6.8 under semisterile conditions. The final fermentation broth contains protein at a concentration of 25 g/L. The biomass is concentrated in large sedimentation tanks and then spray-dried. The mass balance equation (Eq. 9.3) shows that large volumes of oxygen are needed and that carbon dioxide and heat must be removed from the reactor. 

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